ORCID Profile
0000-0002-7164-8053
Current Organisation
University of Western Australia
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Electrical and Electronic Engineering | Photonics and Electro-Optical Engineering (excl. Communications) | Biomedical Engineering not elsewhere classified | Vision Science | Biomedical Instrumentation | Optical Technology | Biomedical Engineering |
Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Engineering | Visual Communication | Expanding Knowledge in Technology
Publisher: MDPI AG
Date: 08-08-2023
DOI: 10.3390/BIOM13081230
Abstract: Diabetes affects the structure of the blood vessel walls. Since the blood vessel walls are made of birefringent organized tissue, any change or damage to this organization can be evaluated using polarization-sensitive optical coherence tomography (PS-OCT). In this paper, we used PS-OCT along with the blood vessel wall birefringence index (BBI = thickness/birefringence2) to non-invasively assess the structural integrity of the human retinal blood vessel walls in patients with diabetes and compared the results to those of healthy subjects. PS-OCT measurements revealed that blood vessel walls of diabetic patients exhibit a much higher birefringence while having the same wall thickness and therefore lower BBI values. Applying BBI to diagnose diabetes demonstrated high accuracy (93%), sensitivity (93%) and specificity (93%). PS-OCT measurements can quantify small changes in the polarization properties of retinal vessel walls associated with diabetes, which provides researchers with a new imaging tool to determine the effects of exercise, medication, and alternative diets on the development of diabetes.
Publisher: Optica Publishing Group
Date: 07-04-2003
DOI: 10.1364/OE.11.000782
Abstract: We demonstrate real-time acquisition, processing, and display of tissue structure, birefringence, and blood flow in a multi-functional optical coherence tomography (MF-OCT) system. This is accomplished by efficient data processing of the phase-resolved inteference patterns without dedicated hardware or extensive modification to the high-speed fiber-based OCT system. The system acquires images of 2048 depth scans per second, covering an area of 5 mm in width x 1.2 mm in depth with real-time display updating images in a rolling manner 32 times each second. We present a video of the system display as images from the proximal nail fold of a human volunteer are taken.
Publisher: IEEE
Date: 08-11-2020
Publisher: SPIE
Date: 08-02-2007
DOI: 10.1117/12.702028
Publisher: The Optical Society
Date: 11-10-2016
DOI: 10.1364/OE.24.024213
Publisher: Optica Publishing Group
Date: 08-04-2010
DOI: 10.1364/OE.18.008515
Publisher: Optica Publishing Group
Date: 23-04-2008
DOI: 10.1364/OE.16.006486
Publisher: SPIE
Date: 14-07-2003
DOI: 10.1117/12.477971
Publisher: Optica Publishing Group
Date: 14-11-2005
Abstract: We introduce a method to determine the retinal nerve fiber layer (RNFL) thickness in OCT images based on anisotropic noise suppression and deformable splines. Spectral-Domain Optical Coherence Tomography (SDOCT) data was acquired at 29 kHz A-line rate with a depth resolution of 2.6 mum and a depth range of 1.6 mm. Areas of 9.6x6.4 mm2 and 6.4x6.4 mm2 were acquired in approximately 6 seconds. The deformable spline algorithm determined the vitreous-RNFL and RNFL-ganglion cell/inner plexiform layer boundary, respectively, based on changes in the reflectivity, resulting in a quantitative estimation of the RNFL thickness. The thickness map was combined with an integrated reflectance map of the retina and a typical OCT movie to facilitate clinical interpretation of the OCT data. Large area maps of RNFL thickness will permit better longitudinal evaluation of RNFL thinning in glaucoma.
Publisher: SPIE
Date: 09-06-2011
DOI: 10.1117/12.889307
Publisher: Optica Publishing Group
Date: 15-05-2006
DOI: 10.1364/OE.14.004380
Publisher: Optica Publishing Group
Date: 15-12-2003
DOI: 10.1364/OE.11.003490
Abstract: An ultra-high-speed spectral domain optical Doppler tomography (SD-ODT) system is used to acquire images of blood flow in a human retina in vivo, at 29,000 depth profiles (A-lines) per second and with data acquisition over 99% of the measurement time. The phase stability of the system is examined and image processing algorithms are presented that allow accurate determination of bi-directional Doppler shifts. Movies are presented of human retinal flow acquired at 29 frames per second with 1000 A-lines per frame over a time period of 3.28 seconds, showing accurate determination of vessel boundaries and time-dependent bi-directional flow dynamics in artery-vein pairs. The ultra-high-speed SD-ODT system allows visualization of the pulsatile nature of retinal blood flow, detects blood flow within the choroid and retinal capillaries, and provides information on the cardiac cycle. In summary, accurate video rate imaging of retinal blood flow dynamics is demonstrated at ocular exposure levels below 600 microW.
Publisher: Elsevier BV
Date: 09-2004
Publisher: SPIE
Date: 07-02-2008
DOI: 10.1117/12.764115
Publisher: Optica Publishing Group
Date: 11-2004
DOI: 10.1364/OL.29.002512
Abstract: We present an analysis for polarization-sensitive optical coherence tomography that facilitates the unrestricted use of fiber and fiber-optic components throughout an interferometer and yields s le birefringence, diattenuation, and relative optic axis orientation. We use a novel Jones matrix approach that compares the polarization states of light reflected from the s le surface with those reflected from within a biological s le for pairs of depth scans. The incident polarization alternated between two states that are perpendicular in a Poincaré sphere representation to ensure proper detection of tissue birefringence regardless of optical fiber contributions. The method was validated by comparing the calculated diattenuation of a polarizing sheet, chicken tendon, and muscle with that obtained by independent measurement. The relative importance of diattenuation versus birefringence to angular displacement of Stokes vectors on a Poincaré sphere was quantified.
Publisher: Optica Publishing Group
Date: 15-08-2005
DOI: 10.1364/OL.30.002131
Abstract: We describe a novel microscopy technique for quantitative phase-contrast imaging of a transparent specimen. The technique is based on depth-resolved phase information provided by common path spectral-domain optical coherence tomography and can measure minute phase variations caused by changes in refractive index and thickness inside the specimen. We demonstrate subnanometer level path-length sensitivity and present images obtained on reflection from a known phase object and human epithelial cheek cells.
Publisher: Optica Publishing Group
Date: 2004
Publisher: Optica Publishing Group
Date: 10-11-2020
DOI: 10.1364/BOE.399949
Abstract: Glaucomatous damage can be quantified by measuring the thickness of different retinal layers. However, poor image quality may h er the accuracy of the layer thickness measurement. We determined the effect of poor image quality (low signal-to-noise ratio) on the different layer thicknesses and compared different segmentation algorithms regarding their robustness against this degrading effect. For this purpose, we performed OCT measurements in the macular area of healthy subjects and degraded the image quality by employing neutral density filters. We also analysed OCT scans from glaucoma patients with different disease severity. The algorithms used were: The Canon HS-100’s built-in algorithm, DOCTRAP, IOWA, and FWHM, an approach we developed. We showed that the four algorithms used were all susceptible to noise at a varying degree, depending on the retinal layer assessed, and the results between different algorithms were not interchangeable. The algorithms also differed in their ability to differentiate between young healthy eyes and older glaucoma eyes and failed to accurately separate different glaucoma stages from each other.
Publisher: The Optical Society
Date: 23-12-2014
DOI: 10.1364/OE.22.032406
Publisher: Optica Publishing Group
Date: 20-11-2007
DOI: 10.1364/OE.15.016141
Publisher: SPIE
Date: 07-2004
DOI: 10.1117/12.528352
Publisher: SPIE
Date: 18-04-2017
DOI: 10.1117/12.2275022
Publisher: SPIE
Date: 24-04-2018
DOI: 10.1117/12.2319383
Publisher: SPIE
Date: 18-04-2017
DOI: 10.1117/12.2275020
Publisher: Elsevier BV
Date: 2024
Publisher: SPIE
Date: 08-02-2007
DOI: 10.1117/12.704639
Publisher: SPIE
Date: 07-2004
DOI: 10.1117/12.531400
Publisher: SPIE
Date: 14-06-2002
DOI: 10.1117/12.470480
Publisher: Optica Publishing Group
Date: 11-2003
DOI: 10.1364/OL.28.002067
Abstract: A signal-to-noise ratio (SNR) analysis is presented for optical coherence tomography (OCT) signals in which time-domain performance is compared with that of the spectral domain. A significant SNR gain of several hundredfold is found for acquisition in the spectral domain. The SNR benefit is demonstrated experimentally in a hybrid time-domain-spectral-domain OCT system.
Publisher: SPIE-Intl Soc Optical Eng
Date: 14-02-2017
Publisher: SPIE
Date: 13-04-2005
DOI: 10.1117/12.592864
Publisher: SPIE
Date: 07-03-2019
DOI: 10.1117/12.2510838
Publisher: SPIE
Date: 08-02-2007
DOI: 10.1117/12.701960
Publisher: Optica Publishing Group
Date: 02-03-2009
DOI: 10.1364/OE.17.004095
Publisher: Optica Publishing Group
Date: 14-02-2022
DOI: 10.1364/BOE.446169
Abstract: Polarization-sensitive optical coherence tomography (PS-OCT) derived birefringence values effectively identify skeletal muscle structural disruption due to muscular dystrophy and exercise-related muscle damage in animal models in ex vivo tissue. The purpose of this investigation was to determine if a PS-OCT needle probe inserted into the leg of a human subject could accurately identify various anatomical structures with implications for use as a diagnostic tool for the determination of skeletal muscle pathology. A healthy middle-aged subject participated in this study. A custom-built PS-OCT system was interfaced with a side-viewing fiber-optic needle probe inserted into the subject’s vastus lateralis muscle via a motorized stage for 3D data acquisition via rotation and stepwise pullback. The deepest recorded PS-OCT images correspond to a depth of 6 mm beneath the dermis with structural images showing uniform, striated muscle tissue. Multiple highly birefringent band-like structures with definite orientation representing connective tissue of the superficial aponeurosis appeared as the depth of the needle decreased. Superficial to these structures the dominating appearance was that of adipose tissue and low birefringent but homogeneous scattering tissue. The data indicate that a PS-OCT needle probe can be inserted into live human skeletal muscle for the identification of relevant anatomical structures that could be utilized to diagnose significant skeletal muscle pathology.
Publisher: The Optical Society
Date: 06-01-2015
DOI: 10.1364/BOE.6.000297
Publisher: Elsevier BV
Date: 09-2004
Publisher: Optica Publishing Group
Date: 30-06-2022
DOI: 10.1364/JOSAA.458631
Abstract: Two designs with a multiplexed superluminescent diode for ultra-high-resolution spectral-domain polarization-sensitive optical coherence tomography (UHR-PS-OCT) are introduced. In the first design, a Wollaston prism separates orthogonal polarization states next to each other on one linescan camera the other design uses a beam displacer to separate orthogonal states onto two lines of a linescan camera with multiple rows of detectors. The coherence lengths measured with the two systems were 3.6 µm and 2.9 µm ( n = 1.38 ), respectively. Measurements were collected from the fovea of a healthy subject, a healthy subject with astigmatism, and a patient with central serous retinopathy (CSR). A single volumetric scan provides double pass retardance induced by the retinal nerve fiber layer birefringence (RNFL) and its birefringence, the cumulative double pass retardance induced by the Henle fiber layer, and the retardance that is induced by the retinal pigment epithelium–Bruch’s membrane complex. The high axial resolution in UHR-PS-OCT is particularly helpful for the measurements of thin retinal tissue, such as the RNFL in the fovea, where birefringence values of around 1°/µm were found. Tilting of the retina due to a CSR or by off centering the imaging beam in the pupil causes an artificial increase in the double pass retardance induced by the RNFL and Henle fiber layer.
Publisher: The Optical Society
Date: 09-04-2015
DOI: 10.1364/BOE.6.001632
Publisher: Optica Publishing Group
Date: 10-2005
DOI: 10.1364/OL.30.002587
Abstract: We present a generalized analysis of fiber-based polarization-sensitive optical coherence tomography with an emphasis on determination of s le optic axis orientation. The polarization properties of a fiber-based system can cause an overall rotation in a Poincaré sphere representation such that the plane of possible measured s le optic axes for linear birefringence and diattenuation no longer lies in the QU-plane. The optic axis orientation can be recovered as an angle on this rotated plane, subject to an offset and overall indeterminacy in sign such that only the magnitude, but not the direction, of a change in orientation can be determined. We discuss the accuracy of optic axis determination due to a fundamental limit on the accuracy with which a polarization state can be determined as a function of signal-to-noise ratio.
Publisher: SPIE-Intl Soc Optical Eng
Date: 2004
DOI: 10.1117/1.1627774
Abstract: Glaucoma causes damage of the nerve fiber layer, which may cause loss of retinal birefringence. Therefore, PS-OCT is a potentially useful technique for the early detection of glaucoma. We built a fiber-based PS-OCT setup that produces real-time images of the human retina in vivo, coregistered with retinal video images of the location of PS-OCT scans. Preliminary measurements of a healthy volunteer show that the double-pass phase retardation per unit of depth of the RNFL is not constant and varies with location, with values between 0.18 and 0.37 deg/microm. A trend in the preliminary measurements shows that the nerve fiber layer located inferior and superior to the optic nerve head is more birefringent than the thinner layer of nerve fiber tissue in the temporal and nasal regions.
Publisher: SPIE
Date: 09-02-2006
DOI: 10.1117/12.649095
Publisher: Optica Publishing Group
Date: 31-05-2004
Abstract: We present the first ultrahigh-resolution optical coherence tomography (OCT) structural intensity images and movies of the human retina in vivo at 29.3 frames per second with 500 A-lines per frame. Data was acquired at a continuous rate of 29,300 spectra per second with a 98% duty cycle. Two consecutive spectra were coherently summed to improve sensitivity, resulting in an effective rate of 14,600 A-lines per second at an effective integration time of 68 micros. The turn-key source was a combination of two super luminescent diodes with a combined spectral width of more than 150 nm providing 4.5 mW of power. The spectrometer of the spectraldomain OCT (SD-OCT) setup was centered around 885 nm with a bandwidth of 145 nm. The effective bandwidth in the eye was limited to approximately 100 nm due to increased absorption of wavelengths above 920 nm in the vitreous. Comparing the performance of our ultrahighresolution SD-OCT system with a conventional high-resolution time domain OCT system, the A-line rate of the spectral-domain OCT system was 59 times higher at a 5.4 dB lower sensitivity. With use of a software based dispersion compensation scheme, coherence length broadening due to dispersion mismatch between s le and reference arms was minimized. The coherence length measured from a mirror in air was equal to 4.0 microm (n= 1). The coherence length determined from the specular reflection of the foveal umbo in vivo in a healthy human eye was equal to 3.5 microm (n = 1.38). With this new system, two layers at the location of the retinal pigmented epithelium seem to be present, as well as small features in the inner and outer plexiform layers, which are believed to be small blood vessels. ?2004 Optical Society of America.
Publisher: SPIE
Date: 08-02-2007
DOI: 10.1117/12.701512
Publisher: Optica Publishing Group
Date: 10-07-2020
DOI: 10.1364/OL.396442
Abstract: In this Letter, we describe a single-pixel polarization-sensitive imaging technique, capable of generating the birefringence map of a thin specimen by using single-pixel detectors. Spatially modulated light is circularly polarized to illuminate the specimen. The transmitted light through the specimen is then focused via a lens and measured by position-sensitive detectors in two orthogonal polarization channels. The measurement of the irradiance and centroid position of the optical focus and subsequent computations enable the production of polarization-dependent wavefront maps, which can then be utilized to reconstruct s le birefringence information. We demonstrate the feasibility of our method by measuring distribution of optic-axis orientation and phase retardation of various birefringent s les.
Publisher: SPIE
Date: 07-2004
DOI: 10.1117/12.529593
Publisher: SPIE
Date: 13-06-2002
DOI: 10.1117/12.470592
Publisher: SPIE
Date: 07-2004
DOI: 10.1117/12.531397
Publisher: Optica Publishing Group
Date: 2007
DOI: 10.1364/OE.15.002421
Abstract: Polarization-sensitive optical coherence tomography can be used to measure the birefringence of biological tissue such as the human retina. Previous measurements with a time-domain polarization-sensitive optical coherence tomography system revealed that the birefringence of the human retinal nerve fiber layer is not constant, but varies as a function of location around the optic nerve head. Here we present a spectral-domain polarization-sensitive optical coherence tomography system that uses a spectrometer configuration with a single line scan camera and a Wollaston prism in the detection arm. Since only one camera has to be synchronized with other components in the system, the design is simplified considerably. This system is 60 times faster than a time-domain polarization-sensitive optical coherence tomography system. Data was acquired using concentric circular scans around the optic nerve head of a young healthy volunteer and the acquisition time for 12 circular scans was reduced from 72 s to 1.2 s. The acquired data sets demonstrate variations in retinal thickness and double pass phase retardation per unit depth that were similar to data from the same volunteer taken with a time-domain polarization-sensitive system. The double pass phase retardation per unit depth of the retinal nerve fiber layer varied between 0.18 and 0.40 degrees/mum, equivalent to a birefringence of 2.2 * 10(-4) and 4.8 * 10(-4) respectively, measured at 840 nm.
Publisher: Optica Publishing Group
Date: 24-01-2020
DOI: 10.1364/BOE.382755
Abstract: The organization of fibrillar tissue on the micrometer scale carries direct implications for health and disease but remains difficult to assess in vivo . Polarization-sensitive optical coherence tomography measures birefringence, which relates to the microscopic arrangement of fibrillar tissue components. Here, we demonstrate a critical improvement in leveraging this contrast mechanism by employing the improved spatial resolution of focus-extended optical coherence microscopy (1.4 µm axially in air and 1.6 µm laterally, over more than 70 µm depth of field). Vectorial birefringence imaging of sheep cornea ex vivo reveals its lamellar organization into thin sections with distinct local optic axis orientations, paving the way to resolving similar features in vivo .
Publisher: SPIE
Date: 26-03-2013
DOI: 10.1117/12.2004165
Publisher: Elsevier BV
Date: 07-2022
DOI: 10.1016/J.RESP.2022.103884
Abstract: Clinical visualization and quantification of the amount and distribution of airway smooth muscle (ASM) in the lungs of in iduals with asthma has major implications for our understanding of airway wall remodeling as well as treatments targeted at the ASM. This paper theoretically investigates the feasibility of quantifying airway wall thickness (focusing on the ASM) throughout the lung in vivo by means of bronchoscopic polarization-sensitive optical coherence tomography (PS-OCT). Using extensive human biobank data from subjects with and without asthma in conjunction with a mathematical model of airway compliance, we define constraints that airways of various sizes pose to any endoscopic imaging technique and how this is impacted by physiologically relevant processes such as constriction, inflation and deflation. We identify critical PS-OCT system parameters and pinpoint parts of the airway tree that are conducive to successful quantification of ASM. We further quantify the impact of breathing and ASM contraction on the measurement error and recommend strategies for standardization and normalization.
Publisher: SPIE
Date: 04-2005
DOI: 10.1117/12.589862
Publisher: SPIE
Date: 07-2004
DOI: 10.1117/12.531395
Publisher: Optica Publishing Group
Date: 02-12-2009
DOI: 10.1364/OE.17.023085
Publisher: SPIE-Intl Soc Optical Eng
Date: 2007
DOI: 10.1117/1.2764460
Abstract: Accurate wavelength assignment of each spectral element for spectral-domain optical coherence tomography (SD-OCT) and optical frequency domain imaging (OFDI) is required for proper construction of biological tissue cross-sectional images. This becomes more critical for functional extensions of these techniques, especially in polarization-sensitive optical coherence tomography (PS-OCT), where incorrect wavelength assignment between the two orthogonal polarization channels leads to polarization artifacts. We present an autocalibration method for wavelength assignment that does not require separate calibration measurements and that can be applied directly on actual data. Removal of the birefringence artifact is demonstrated in a PS-OCT system with picometer accuracy in the relative wavelength assignment, resulting in a residual phase error of 0.25 deg/100 microm. We also demonstrate, for the first time, a quantitative birefringence map of an in vivo human retinal nerve fiber layer.
Publisher: SPIE
Date: 07-2004
DOI: 10.1117/12.531393
Publisher: SPIE
Date: 07-2003
DOI: 10.1117/12.478966
Publisher: Optica Publishing Group
Date: 19-02-2020
DOI: 10.1364/BOE.378506
Abstract: Terahertz (THz) imaging and optical coherence tomography (OCT) provide complementary information with similar length scales. In addition to OCT’s extensive use in ophthalmology, both methods have shown some promise for other medical applications and non-destructive testing. In this paper, we present an iterative algorithm that combines the information from OCT and THz imaging at two different measurement locations within an object to determine both the depth of the reflecting layers at the two locations and the unknown refractive index of the medium for both the OCT wavelengths and THz frequencies. We validate this algorithm using a silicone test object with embedded layers and show that the depths and refractive index values obtained from the algorithm agreed with the measured values to within 3.3%. We further demonstrate for the first time that OCT and THz images can be co-registered and aligned using unsupervised image registration. Hence we show that a combined OCT/THz system can provide unique information beyond the capability of the separate modalities alone, with possible applications in the medical, industrial and pharmaceutical sectors.
Publisher: Optica Publishing Group
Date: 16-07-2021
DOI: 10.1364/BOE.434812
Abstract: Selective retinal therapy (SRT) employs a micro-second short-pulse lasers to induce localized destruction of the targeted retinal structures with a pulse duration and power aimed at minimal damage to other healthy retinal cells. SRT has demonstrated a great promise in the treatment of retinal diseases, but pulse energy thresholds for effective SRT procedures should be determined precisely and in real time, as the thresholds could vary with disease status and patients. In this study, we present the use of a multi-port fiber-based interferometer (MFI) for highly sensitive real-time SRT monitoring. We exploit distinct phase differences among the fiber ports in the MFI to quantitatively measure localized fluctuations of complex-valued information during the SRT procedure. We evaluate several metrics that can be computed from the full complex-valued information and demonstrate that the complex contour integration is highly sensitive and most correlative to pulse energies, acoustic outputs, and cell deaths. The validity of our method was demonstrated on excised porcine retinas, with a sensitivity and specificity of 0.92 and 0.88, respectively, as compared with the results from a cell viability assay.
Publisher: American Thoracic Society
Date: 05-2020
DOI: 10.1164/AJRCCM-CONFERENCE.2020.201.1_MEETINGABSTRACTS.A1240
Publisher: Wiley
Date: 11-03-2019
Abstract: As data acquisition for retinal imaging with optical coherence tomography (OCT) becomes faster, efficient collection of photons becomes more important to maintain image quality. One approach is to use a larger aperture at the eye's pupil to collect more photons that have been reflected from the retina. A 2.8-mm beam diameter system with only seven reflecting surfaces was developed for low-loss retinal imaging. The larger beam size requires defocus and astigmatism correction, which was done in a closed loop adaptive optics method using a Shack-Hartmann wavefront sensor and a deformable mirror (DM) with 140 actuators and a ±2.75 μm stroke. This DM facilitates defocus correction ranging from approximately -3 D to +3 D. Comparing the new system with a standard 1.2-mm system on a model eye, a signal-to-noise gain of 4.5 dB and a 2.3 times smaller speckle size were measured. Measurements on the retinas of five subjects showed even better results, with increases in dynamic range up to 13 dB. Note that the new s le arm only occupies 30 cm × 60 cm, which makes it highly suitable for imaging in a clinical environment. Figure: B-scan images obtained over a width of 8 deg from the right eye of a 31-year-old Caucasian male. While the left side was imaged with a standard 1.2-mm OCT system, the right side was imaged with the 2.8-mm system. Both images were collected with the same integration time and incident power, after correction of aberrations. Using the dynamic range within the images, which is determined by comparing the highest pixel value to the noise floor, a difference in dynamic range of 10.8 dB was measured between the two systems.
Publisher: SPIE
Date: 11-02-2010
DOI: 10.1117/12.846585
Publisher: Optica Publishing Group
Date: 11-11-2009
DOI: 10.1364/OE.17.021634
Publisher: Optica Publishing Group
Date: 23-06-2021
DOI: 10.1364/BOE.426079
Abstract: A new method based on polarization-sensitive optical coherence tomography (PS-OCT) is introduced to determine the polarization properties of human retinal vessel walls, in vivo . Measurements were obtained near the optic nerve head of three healthy human subjects. The double pass phase retardation per unit depth (DPPR/UD), which is proportional to the birefringence, is higher in artery walls, presumably because of the presence of muscle tissue. Measurements in surrounding retinal nerve fiber layer tissue yielded lower DPPR/UD values, suggesting that the retinal vessel wall tissue near the optic nerve is not covered by retinal nerve fiber layer tissue (0.43°/µm vs. 0.77°/µm, respectively). Measurements were obtained from multiple artery-vein pairs, to quantify the different polarization properties. Measurements were taken along a section of the vessel wall, with changes in DPPR/UD up to 15%, while the vessel wall thickness remained relatively constant. A stationary scan pattern was applied to determine the influence of involuntary eye motion on the measurement, which was significant. Measurements were also analyzed by two examiners, with high inter-observer agreement. The measurement repeatability was determined with measurements that were acquired during multiple visits. An improvement in accuracy can be achieved with an ultra-broad-bandwidth PS-OCT system since it will provide more data points in-depth, which reduces the influence of discretization and helps to facilitate better fitting of the birefringence data.
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.877225
Publisher: Optica Publishing Group
Date: 30-05-2005
Abstract: We demonstrate a high-speed multi-functional spectral-domain optical coherence tomography system, using a broadband light source centered at 1.3 microm and two InGaAs line scan cameras capable of acquiring in idual axial scans in 24.4 micros, at a rate of 18,500 axial scans per second. Fundamental limitations on the accuracy of phase determination as functions of signal-to-noise ratio and lateral scan speed are presented and their relative contributions are compared. The consequences of phase accuracy are discussed for both Doppler and polarization-sensitive OCT measurements. A birefringence artifact and a calibration procedure to remove this artifact are explained. Images of a chicken breast tissue s le acquired with the system were compared to those taken with a time-domain OCT system for birefringence measurement verification. The ability of the system to image pulsatile flow in the dermis and to perform functional imaging of large volumes demonstrates the clinical potential of multifunctional spectral-domain OCT.
Publisher: SPIE
Date: 09-02-2006
DOI: 10.1117/12.649064
Publisher: SPIE
Date: 13-07-2004
DOI: 10.1117/12.532717
Publisher: Optica Publishing Group
Date: 09-02-2004
Abstract: An ultra-high-speed spectral-domain optical coherence tomography system (SD-OCT) was developed for imaging the human retina and optic nerve in vivo at a sustained depth profile (A-line) acquisition speed of 29 kHz. The axial resolution was 6 microm in tissue and the system had shot-noise-limited performance with a maximum sensitivity of 98.4 dB. 3-dimensional data sets were collected in 11 and 13 seconds for the macula and optic nerve head respectively and are presented to demonstrate the potential clinical applications of SD-OCT in ophthalmology. Additionally, a 3-D volume of the optic nerve head was constructed from the acquired data and the retinal vascular network was visualized.
Publisher: The Optical Society
Date: 19-12-2018
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 08-2004
DOI: 10.1167/IOVS.03-1160
Publisher: Elsevier BV
Date: 08-2011
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 09-08-2011
DOI: 10.1167/IOVS.10-6424
Publisher: Optica Publishing Group
Date: 20-05-2008
DOI: 10.1364/OE.16.008126
Publisher: American Medical Association (AMA)
Date: 12-2200
DOI: 10.1001/ARCHOPHT.123.12.1715
Abstract: To introduce a new ophthalmic optical coherence tomography technology that allows unprecedented simultaneous ultra-high speed and ultra-high resolution. Using a superluminescent diode source, a clinically viable ultra-high speed, ultra-high resolution spectral domain optical coherence tomography system was developed. In vivo images of the retina, the optic nerve head, and retinal blood flow were obtained at an ultra-high speed of 34.1 microseconds (ms) per A-scan, which is 73 times faster than commercially available optical coherence tomography instruments. Single images (B-scans) consisting of 1000 A-scans were acquired in 34.1 ms, allowing video rate imaging at 29 frames per second with an axial resolution of 6 mum. Using a different source in a slightly slower configuration, single images consisting of 500 A-scans were acquired in 34 ms, allowing imaging at 29 frames per second at an axial resolution of 3.5 microm, which is 3 times better than commercially available optical coherence tomography instruments. The amount of energy directed into the eye in both cases, 600 microW, is less than that of the Stratus OCT3 and is safe for intrabeam viewing for up to 8 hours at the same retinal location. Spectral domain optical coherence tomography technology enables ophthalmic imaging with unprecedented simultaneous ultra-high speed and ultra-high resolution.
Publisher: Optica Publishing Group
Date: 26-02-2010
DOI: 10.1364/OE.18.005257
Publisher: The Optical Society
Date: 07-10-2016
DOI: 10.1364/BOE.7.004490
Publisher: SPIE
Date: 07-2003
DOI: 10.1117/12.478971
Publisher: Optica Publishing Group
Date: 05-07-2023
DOI: 10.1364/BOE.488822
Abstract: Polarization-sensitive optical coherence tomography (PS-OCT) measures the polarization states of the backscattered light from tissue that can improve angiography based on conventional optical coherence tomography (OCT). We present a feasibility study on PS-OCT integrated with deep learning for PS-OCT angiography (PS-OCTA) imaging of human cutaneous microvasculature. Two neural networks were assessed for PS-OCTA, including the residual dense network (RDN), which previously showed superior performance for angiography with conventional OCT and the upgraded grouped RDN (GRDN). We also investigated different protocols to process the multiple signal channels provided by the Jones matrices from the PS-OCT system to achieve optimal PS-OCTA performance. The training and testing of the deep learning-based PS-OCTA were performed using PS-OCT scans collected from 18 skin locations comprising 16,600 B-scan pairs. The results demonstrated a moderately improved performance of GRDN over RDN, and of the use of the combined signal from the Jones matrix elements over the separate use of the elements, as well as a similar image quality to that provided by speckle decorrelation angiography. GRDN-based PS-OCTA also showed ∼2-3 times faster processing and improved mitigation of tissue motion as compared to speckle decorrelation angiography, and enabled fully automatic processing. Deep learning-based PS-OCTA can be used for imaging cutaneous microvasculature, which may enable easy adoption of PS-OCTA for preclinical and clinical applications.
Publisher: SPIE
Date: 07-2003
DOI: 10.1117/12.479027
Publisher: SPIE-Intl Soc Optical Eng
Date: 2004
DOI: 10.1117/1.1645797
Abstract: Optical coherence tomography enables cross-sectional imaging of tissue structure to depths of around 1.5 mm, at high-resolution and in real time. Incorporation of polarization sensitivity (PS) provides an additional contrast mechanism which is complementary to images mapping backscattered intensity only. We present here polarization-sensitive optical coherence tomography (OCT) images of human skin in vivo, demonstrating the ability of the technique to visualize and quantify the birefringent properties of skin. Variation in normal skin birefringence according to anatomical location is demonstrated, and discussed in relation to collagen distribution at each location. From measurements on a s le of five human volunteers, mean double-pass phase retardation rates of 0.340+/-0.143, 0.250+/-0.076, and 0.592+/-0.142 deg/microm were obtained for the dorsal hand, temple, and lower back regions, respectively. We demonstrate how averaging the Stokes parameters of backscattered light over a range of axial and lateral dimensions results in a reduction of speckle-induced noise. Ex les of PS-OCT images from skin sites following wound healing and repair are also presented and discussed.
Publisher: SPIE
Date: 13-04-2005
DOI: 10.1117/12.592840
Publisher: Optica Publishing Group
Date: 03-2004
DOI: 10.1364/OL.29.000480
Abstract: An ultrahigh-speed spectral domain optical coherence tomography (SD-OCT) system is presented that achieves acquisition rates of 29,300 depth profiles/s. The sensitivity of SD-OCT and time domain OCT (TD-OCT) are experimentally compared, demonstrating a 21.7-dB improvement of SD-OCT over TD-OCT. In vivo images of the human retina are presented, demonstrating the ability to acquire high-quality structural images with an axial resolution of 6 microm at ultrahigh speed and with an ocular exposure level of less than 600 microW.
Publisher: IEEE
Date: 28-08-2022
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.874473
Publisher: Wiley
Date: 26-02-2018
Publisher: The Optical Society
Date: 10-2013
DOI: 10.1364/BOE.4.002296
Publisher: SPIE
Date: 13-07-2004
DOI: 10.1117/12.529627
Publisher: Elsevier BV
Date: 06-2006
DOI: 10.1016/J.AJO.2006.01.086
Abstract: To correlate in vivo human retina optical coherence tomography (OCT)3 images with histology. Case series. Linear OCT3 scans through the macula and optic nerve were obtained in three eyes of three patients who then underwent exenteration surgery for orbital cancers. OCT3 images were then correlated with histology. On histology, two eyes were normal, and one eye had dry macular degeneration. The plexiform layers on histology correlated with the green/yellow areas on the OCT3 scans, and the nuclear layers correlated with the black areas on the OCT3 scans. The authors are unaware of previous reports correlating histology to in vivo human retina OCT3 images. Our findings using human eyes are not different from previous animal studies, in that the plexiform layers are optically highly backscattering and the nuclear layers are not.
Publisher: Optica Publishing Group
Date: 09-2002
DOI: 10.1364/OL.27.001534
Abstract: We demonstrate that tissue structure, birefringence, and blood flow can be imaged simultaneously by use of techniques of polarization-sensitive optical coherence tomography and phase-resolved optical Doppler tomography. An efficient data-acquisition procedure is implemented that optimizes the concurrent processing and display of all three image types. Images of in vivo human skin acquired with a high-speed fiber-based system are presented.
Publisher: Optica Publishing Group
Date: 15-09-2002
DOI: 10.1364/OL.27.001610
Abstract: To our knowledge, this is the first demonstration of in vivo depth-resolved birefringence measurements of the human retinal nerve fiber layer (RNFL) by use of polarization-sensitive optical coherence tomography (PS-OCT). Because glaucoma causes nerve fiber layer damage, which may cause loss of retinal birefringence, PS-OCT is a potentially useful technique for the early detection of glaucoma. We built a fiber-based PS-OCT setup that produces quasi-real-time images of the human retina in vivo . Preliminary measurements of a healthy volunteer showed that the double-pass phase retardation per unit depth of the RNFL near the optic nerve head is 39+/-6( degrees )/100microm .
Start Date: 10-2021
End Date: 10-2023
Amount: $192,500.00
Funder: Australian Research Council
View Funded ActivityStart Date: 02-2022
End Date: 02-2025
Amount: $311,042.00
Funder: Australian Research Council
View Funded Activity